Cylindrical filtration units, containing replaceable cartridges made of fibrous material through which liquids are circulated under pressure to be cleaned, have been known for many years. Effective filtration depends upon passing all of the liquid through the filter cartridge so as to exclude whatever contamination liquids or solids may be present in the liquid to be filtered. Any liquid bypassing the filter cartridge to an appreciable extent is unlikely to become as clean as liquid traversing a longer path through the filter.
Filters of this general type are disclosed in such U.S. patents as Bridges et al. U.S. Pat. No. 4,366,057, and Rasmussen U.S. Pat. No. 4,780,204 and U.S. Pat. No. 4,792,397. Their filter cartridges are of wound type, variously constructed to enhance the likelihood of axial flow predominating over radial flow.
A need remains for more positive axial flow enhancement and to provide for interim storage of separated water or like contaminant. The present invention is designed to meet these needs.